An emergency energy storage power supply system for local ventilation fans in coal mines

Abstract

The present invention is an emergency energy storage power supply system for local ventilators in coal mines. The system includes a battery part, an inverter unit, a transformer unit, an information collection unit, a charging unit, a control unit, a display unit, a key unit and a local ventilator; the connection relationship is as follows: the control unit is respectively connected to the battery part, the display unit, the key unit, the information collection unit, the charging unit and the inverter unit; the battery part, the inverter unit, the transformer unit and the local ventilator are connected in sequence; the information collection unit is also respectively connected to the battery part, the inverter unit, the transformer unit and the local ventilator; the battery part is connected to the charging unit. The present invention can improve the quality of electric energy, reduce the damage of harmonics to the ventilator, reduce reactive power loss and reduce heat generation.

Description

Technical Field

[0001] The design of the invention belongs to the technology of coal mine power supply equipment, and is used for local ventilators of coal mine excavation working faces and as emergency power supply for local ventilators when coal mine power grid fails. Background Art

[0002] Safety in production is the top priority of coal mine production. Coal mines are prone to gas explosions caused by excessively high gas concentrations, which can cause huge economic losses and casualties. Uninterrupted ventilation is required in coal mine excavation working faces. Due to the harsh working environment of coal mines, humidity underground, and improper operation of workers, it is easy to cause problems such as underground power supply line failures, local fan failures, and equipment aging, resulting in power outages and wind stoppages at the working face, affecting the normal production work and the life safety of workers. This requires the power supply system to not only provide high-quality power quality to the load, but also to ensure the continuity of power supply, ensure that there are timely backup plans after failures of the underground power grid and local fans, retain sufficient time margins, provide time for maintenance personnel to overhaul, and ventilate the working face in time to prevent gas accumulation and explosion accidents. Therefore, it is very necessary to design and research an emergency energy storage power supply system for local fans in coal mines.

[0003] The existing local ventilator system does not have a filter, and the output voltage waveform is a square wave, with serious voltage harmonics. Serious harmonics will affect the service life of the ventilator and easily cause failure. For example, the patent "An emergency power supply device for coal mine excavation working face" Patent No. CN104242434 provides an emergency power supply device for the local ventilator of the coal mine excavation working face when the power is off. Its technical solution is: It consists of an emergency power supply part and a control part, which are roughly composed of a battery part, a charging unit, a control unit, a frequency converter, and a local ventilator. The connection relationship is as follows: Fig.10 As shown. Its working mechanism is to convert the direct current of the battery through the inverter to a voltage that can drive the local ventilator. The battery of this patent is composed of 276 lithium-ion batteries connected in series, with a voltage range of 690V-1035V. The inverter has no filter and the output voltage waveform is a square wave. The device has many battery packs in series, large volume, inflexible use, high battery voltage level, and certain danger. The inverter output voltage harmonics are large, which will cause certain damage to the local ventilator, waste battery energy, and generate large heat.

[0004] The present invention designs an LCL filter using transformer leakage inductance to filter the square wave output by the inverter and improve the quality of electric energy. The underground power grid of a coal mine is 660V / 1140V. The existing local ventilator directly inverts the battery to 660V / 1140V, which requires a higher DC bus voltage, resulting in a large volume of energy storage batteries and high cost. The present invention adopts a transformer boosting method to boost the inverted voltage to the rated voltage of the local ventilator motor through a step-up transformer, which reduces the volume, is flexible to use, and reduces cost. Summary of the invention

[0005] The purpose of the present invention is to provide an emergency energy storage power supply system for local ventilators in coal mines, aiming at the problem that gas accumulation is prone to occur after power failure and ventilation stop at the current coal mine excavation working face. The system uses the inductance of the transformer and the filter to form an LCL filter circuit, thereby improving the quality of electric energy; by bidirectional time-sharing multiplexing of the transformer, the taps on the high-voltage side of the transformer are used with different combinations of contactors to switch the high-voltage side in Y / △, and when the main and standby fans in the mine are powered off or fail, the system is started in time according to the start time required by the working face, and the underground high-power local ventilator is dragged to ventilate the working face; the system uses a 320V lead-acid battery that meets the coal mine safety regulations as a DC source to provide energy for the system; an IGBT is used to invert the DC voltage into 220V / 50Hz AC, and the inverted AC is boosted to 660V through a step-up transformer, meeting the voltage use conditions of the high-power local ventilator in the coal mine, and providing the local ventilator with a power supply condition with high power quality. The emergency energy storage power supply system of local ventilation fans in coal mines supplies power to high-power standby fans underground, ensuring the normal operation of the working face fans and uninterrupted ventilation, avoiding accidents such as gas accumulation and gas explosion in the mine, and ensuring the safety of underground production work.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] An emergency energy storage power supply system for a local ventilator in a coal mine, the system comprising a battery part, an inverter unit, a transformer unit, an information collection unit, a charging unit, a control unit, a display unit, a key unit and a local ventilator;

[0008] The connection relationship is as follows: the control unit is connected to the battery part, the display unit, the key unit, the information collection unit, the charging unit, and the inverter unit respectively; the battery part, the inverter unit, the transformer unit, and the local ventilator are connected in sequence; the information collection unit is also connected to the battery part, the inverter unit, the transformer unit, and the local ventilator respectively; the battery part is connected to the charging unit;

[0009] In the transformer unit, the transformer ratio is 220V / 660V or 380V / 1140V; its composition is that U1, V1, W1 are the taps on the low-voltage side of the transformer, which are star-connected; U2, V2, W2 are the taps on the high-voltage side of the transformer, when the contactors A1, A2, A3 are closed, the high-voltage side is star-connected, and when the contactors B1, B2, B3 are closed, the high-voltage side is delta-connected.

[0010] The display unit is a TFT color screen, and the key unit is a 485 bus 16-way input and output motherboard; both use RS-485 communication.

[0011] The inverter unit includes two contactors S1 and S2, two capacitors C1 and C2, six IGBT modules (each IGBT module includes an upper bridge arm and a lower bridge arm), three filter capacitors and three filter inductors; wherein the positive electrode of the power supply is connected to one end of the contactor S1, the other end of the contactor S1 is connected in series with one end of the contactor S2, and the contactor S2 is also connected in parallel with a resistor; the capacitor C1 and the capacitor C2 are connected in series, the positive electrode of the capacitor C1 is connected to the other end of the contactor S2, the negative electrode of the capacitor C1 is connected to the The positive electrode is connected, and the negative terminal of capacitor C2 is connected to the negative electrode of the power supply; 6 IGBTs are connected in parallel, the positive electrode of each IGBT is connected to the positive electrode of capacitor C1, and the negative electrode is connected to the negative electrode of capacitor C2, among which T1 and T2 are a group, and the output ends of T1 and T2 are connected together; T3 and T4 are a group, and the output ends of T3 and T4 are connected together; T5 and T6 are a group, and the output ends of T5 and T6 are connected together; the output ends of each group are respectively connected in series with filter inductors L1, L2, and L3; the filter capacitors are respectively connected in parallel after the filter inductors.

[0012] The charging unit is composed of a 1140V / 380V step-down transformer and a DC charger, the input end of the DC charger is connected to the tap of the low-voltage side of the step-down transformer, and the output end is connected to the battery part;

[0013] The battery part is specifically a 320V lead-acid battery composed of 160 lead-acid batteries connected in series that meet the coal mine safety regulations.

[0014] The operating method of the emergency energy storage power supply system for a local ventilation fan in a coal mine comprises the following steps:

[0015] Step 1: Check if there is a fault:

[0016] The voltage sensor and current sensor in the information collection unit collect the status of the main and standby power supply in the coal mine in real time, and transmit the information to the control unit (MCU), which determines whether there is a fault; the MCU determines whether the voltage sensor has an AC voltage greater than 600V. If it exists, the main and standby power supply is not faulty, otherwise the main and standby power supply is faulty;

[0017] When the main and standby power supplies in the coal mine are fault-free, the transformer high-voltage side tap contactors in the transformer unit, B1, B2, B3 are closed, and A1, A2, A3 are disconnected; at this time, the transformer high-voltage side is connected in a triangle, used as a step-down transformer, to power the DC charger, and the charger charges the battery; the battery is always in a floating charge state, and when the battery power is within a certain range, the MCU controls the contactor to stop charging;

[0018] When the main and standby power supplies in the coal mine fail, run step 2;

[0019] Step 2: The control unit (MCU) controls the transformer high-voltage side tap contactors A1, A2, A3 in the transformer unit to close, and B1, B2, B3 to disconnect. At this time, the transformer high-voltage side is star-connected, and the output voltage of the inverter module is inverted; the MCU controls the contactors S1 and S2 of the inverter unit to close, and pre-charge the capacitors C1 and C2 for energy buffering;

[0020] Step 3:

[0021] Step 3.1: After the contactor of the inverter unit is closed, the control unit (MCU) synthesizes the three-phase electricity with a time phase difference of 120° into a space voltage vector U ref MCU calculates formula (1) and formula (2) to determine the space voltage vector U ref Sector in which you are located;

[0022]

[0023] Among them, U α , U β are the coordinate axes in the stationary coordinate system after CLARK transformation, and U1, U2, and U3 respectively determine the voltage vector U ref The judgment value of the sector;

[0024] Define U1>0, A=1, otherwise A=0; U2>0, B=1, otherwise B=0; U3>0, C=1, otherwise C=0; the formula for judging the sector is:

[0025] N=4*C+2*B+A (2)

[0026] Step 3.2: MCU calculates the action time of the basic space vector of each sector according to the relationship between the action time of the basic space vector of each sector:

[0027]

[0028]

[0029] Among them, T Sis the time for one cycle of vector action, T1, T2, T3, T4, T5, T6 are the time for each vector action in each sector, U dc is the DC bus voltage, T x is the first vector action time in each sector, T y is the vector action time that occurs later in each sector;

[0030] According to formula (3), the PWM duty cycle corresponding to each period of time is calculated:

[0031]

[0032] Among them, NTPWM is the automatic reload value generated by the MCU for the PWM interrupt; T Nx The PWM duty cycle converted from the first vector action time in each sector; T Ny The PWM duty cycle converted from the vector action time in each sector.

[0033] Then, the PWM duty cycle of each phase IGBT of the inverter unit is calculated according to formula (4).

[0034]

[0035] Among them, N taon N is the duty cycle of the A-phase IGBT receiving PWM; tbon N is the duty cycle of the B-phase IGBT receiving PWM; tcon The duty cycle of the C-phase IGBT receiving PWM.

[0036] The action time of each sector space vector is converted into the duty cycle of PWM, that is, the improved V / F five-stage vector control algorithm is adopted to generate 6-channel PWM;

[0037] Step 3.3: Transmit 6 PWMs to 12 IGBTs. The two upper bridge arms of each phase receive the same PWM, and the lower bridge arms receive the same PWM. The inverter module inverts the DC power output by the battery into three-phase AC power with a certain voltage amplitude and transmits it to the transformer.

[0038] The inductance and capacitance of the inverter module and the inductance of the transformer form an LCL filter, which filters the voltage output by the IGBT to generate alternating current with a phase difference of 120° on the three phases to drive the local ventilator to work.

[0039] The essential features of the present invention are:

[0040] In current technology, the inverter does not add a transformer, but directly supplies power to the electrical appliances. After adding the transformer, a V / F soft start algorithm that is more suitable for indirectly controlling the motor through the transformer needs to be invented. The innovation of this invention lies in the application scenario and indirectly controlling the motor through the transformer, which not only reduces the system volume and increases flexibility, but also reduces the cost of system production and purchase of batteries.

[0041] This patent is a backup coal mine local ventilation fan emergency energy storage power supply system used in the underground coal mine excavation working face. When the underground power grid or the main and standby ventilation fans fail, the start time can be set according to the needs of the coal mine, and the local ventilation fan emergency energy storage power supply system can be started in time to ensure continuous ventilation of the working face. After the underground power grid or the main and standby ventilation fans fail, it will automatically switch to the commonly used fan for ventilation.

[0042] A transformer unit is added to the topological structure of this system design. The input on the low-voltage side of the transformer is 220V, and the output voltage on the high-voltage side is 660V or 1140V. Through the connection of the high-voltage side transformer tap, when the high-voltage side is connected to star 660V, the transformer drives the fan, and the local fan is indirectly controlled by controlling the transformer; when the high-voltage side is connected to triangle, the low-voltage side supplies power to the charger, realizing the bidirectional multiplexing function of the transformer.

[0043] This system uses vector control algorithm and V / F soft start control algorithm to indirectly control the asynchronous motor through an isolation transformer, and improves the traditional V / F control algorithm to make it more suitable for controlling the motor through a transformer.

[0044] Beneficial effects of the present invention:

[0045] The present invention relates to an emergency energy storage power supply system for a local ventilation fan in a coal mine. The system is installed at an underground mining face in a coal mine, and solves the problem of excessive gas concentration caused by power outage or air stoppage due to failure of a coal mine power grid or a main standby fan, and effectively prevents gas accumulation at the mining face, avoids mine gas explosion accidents, and ensures coal mine safety and safe production.

[0046] Compared with the traditional inverter, this system adds a step-up transformer in the topology structure, and adds a filter after the inverter voltage is generated to improve the voltage quality. Adding a transformer can greatly reduce the DC side voltage and the battery voltage, thereby reducing the battery volume, making it more flexible and convenient in transportation and installation, and more convenient and quick to use. It also reduces the cost of purchasing batteries when coal mines purchase equipment and reduces the system production cost.

[0047] The conventional inverter needs a DC side voltage of at least 940V to convert a voltage of 660V; three 320V explosion-proof batteries are required; the present invention only needs one set of 320V batteries.

[0048] This system adopts five-stage vector control in the control algorithm, which reduces the number of switching times of IGBT in each cycle and reduces the heat generated by IGBT; in the starting method of the motor, it adopts the improved V / F soft start control algorithm to reduce the starting current of the fan.

[0049] This system uses five-stage vector control in program control; the temperature rise after 40 minutes of operation with seven-stage is 50℃; the temperature rise after 5-stage is 25℃.

[0050] The communication between the display unit, battery management module and keyboard unit and the control unit of this system all adopts RS-485 communication protocol, which increases the reliability and safety of system control.

[0051] This system is installed and added with a leakage lockout module, which can provide real-time leakage protection for the system; software and hardware protection are added for overvoltage, overcurrent and overtemperature, which increases the reliability and safety of the system operation.

[0052] Attached Figure 7-Figure 9 This is a system effect diagram. This has been described in Example 1. Currently, most inverters on the market do not have filters, and the output is square waves, with a high voltage distortion rate of about 20%. The present invention adds a filter to the system, and the voltage distortion rate is 0.78%, which improves the quality of power.

[0053] The present invention can improve the quality of electric energy, reduce the damage of harmonics to the ventilator, reduce reactive power loss and reduce heat generation. Harmonics will seriously affect the service life of the ventilator and easily cause failure. After improving the quality of electric energy, the safety of system use is increased, the loss is reduced, and the use time of the emergency energy storage power supply is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The present invention is further described below with reference to the accompanying drawings and examples.

[0055] Figure 1 It is the system functional block diagram;

[0056] Figure 2 This is the transformer schematic diagram;

[0057] Figure 3 This is the schematic diagram of the inverter unit;

[0058] Figure 4 It is the functional block diagram of the control unit;

[0059] Figure 5 This is the voltage and frequency relationship diagram of the improved V / F starting method;

[0060] Figure 6 It is the system workflow diagram;

[0061] Figure 7 It is the output voltage and current waveform;

[0062] Figure 8 is the voltage-current vector diagram;

[0063] Fig. 9 is the system output power quality diagram;

[0064] Fig.10 It is the connection relationship diagram of patent CN104242434; DETAILED DESCRIPTION

[0065] The present invention is described in detail below with reference to the accompanying drawings, but is only for illustration rather than limitation of the present invention.

[0066] The present invention is an emergency energy storage power supply system for local ventilation fans in coal mines, which is applied to underground excavation working faces in coal mines. Generally, there are two power supply systems in underground coal mines, which are used to supply power to the common ventilation system and the standby ventilation system. When the two power supply systems or the common and standby ventilation fans fail, the present invention automatically works to ensure normal ventilation of the working face and maintain the air volume requirements of the working face. After the failure is eliminated, the common and standby ventilation systems work and automatically switch to the standby state.

[0067] The coal mine local ventilator emergency energy storage power supply system of the present invention is as follows Figure 1 As shown, it includes a battery part, an inverter unit, a transformer unit, an information collection unit, a charging unit, a control unit, a display unit, a button unit and a local ventilator;

[0068] The connection relationship is as follows: the control unit is connected to the battery part, the display unit, and the key unit respectively through RS-485 communication; the control unit is connected to the information acquisition unit, the charging unit, and the inverter unit through a signal line; the battery part, the inverter unit, the transformer unit, and the local ventilator are connected in sequence; the information acquisition unit is also connected to the battery part, the inverter unit, the transformer unit, and the local ventilator respectively; the battery part is connected to the charging unit;

[0069] The control unit is connected to the inverter unit, and the control unit generates PWM to control the inverter unit to invert the direct current output by the battery part; the battery part is connected to the positive and negative poles of the input end of the inverter unit respectively; the charging unit is connected to the battery part and the control unit; the information acquisition unit is connected to the control unit, and the information acquisition unit collects information such as battery voltage, system output voltage, IGBT temperature, transformer temperature, transformer low-voltage side, transformer high-voltage side current, etc.; the collected information is summarized and converted into a voltage signal and transmitted to the control unit; the output end of the inverter unit is connected to the transformer unit, and the inverter unit generates three-phase alternating current after filtering the generated electric energy, and the electric energy is boosted through a step-up transformer.

[0070] The transformer unit is as follows Figure 2 As shown, the transformer ratio is 220V / 660V or 380V / 1140V; its composition is that U1, V1, W1 are the taps on the low-voltage side of the transformer, which are star-connected; U2, V2, W2 are the taps on the high-voltage side of the transformer, when the contactors A1, A2, A3 are closed, the high-voltage side is star-connected, and when the contactors B1, B2, B3 are closed, the high-voltage side is delta-connected.

[0071] The transformer complies with coal mine safety standards, with a rated capacity of 60KVA, a star connection on the low voltage side, and a star / delta connection on the high voltage side. The transformation ratio is 220V / 660V or 380V / 1140V. The tap on the high voltage side of the transformer is connected by different contactors.

[0072] In the existing emergency power supply, no one uses a transformer as a booster, and indirectly controls the motor by controlling the transformer voltage. This patent uses the inductance of the transformer for filtering to improve the quality of electric energy, and uses the method of time-sharing multiplexing of the transformer. When using time-sharing multiplexing, the contactor is used for switching, which is a new circuit. Although the transformer is a well-known device, its structure and usage are different. The different structures are 660V / 1140V on the high-voltage side, and the winding connection method on the high-voltage side can be changed by controlling the contactor.

[0073] The transformer has a certain inductance, and forms an LCL structure with the filter of the inverter unit to filter and boost the electric energy.

[0074] The underground power grid voltage is generally 660V / 1140V; the use of transformers for voltage boosting reduces the use of power devices, reduces system heat generation, and improves system safety and flexibility; filtering improves power quality, reduces losses, and increases the service life and reliability of the emergency energy storage power supply system for local ventilation fans in coal mines.

[0075] The low-voltage side is a triangle connection, and the high-voltage side is a selectable mode: when the selected output is 660V, the high-voltage side is a star connection; when the selected output is 1140V, the high-voltage side is a triangle connection; the six transformer taps on the high-voltage side are all connected to the contactor, and the Y / △ switching is achieved by controlling different combinations of contactors (Y connection when A1 A2 A3 is closed, and △ connection when B1 B2 B3 is closed); when the high-voltage side is a star connection, that is, the output is 660V, the transformer is used as a step-up transformer to power the fan; when the high-voltage side is a triangle connection, that is, the high-voltage side is an input of 1140V, the transformer is used as a step-down transformer to power the DC charger; when the transformer is used as a step-up transformer, the inductance of the transformer is used to form an LCL filter circuit with the filter (the filter is three filter inductors connected in series after each group of IGBT outputs in the inverter unit and three filter capacitors are connected in parallel as a filter) to improve the quality of power.

[0076] The state display unit is a TFT color screen, and the key unit is a 485 bus 16-way input and output motherboard; both use RS-485 communication.

[0077] The inverter unit is as follows Figure 3 As shown, it includes 2 contactors S1 and S2, 2 capacitors C1 and C2, 6 IGBT modules (each IGBT module includes an upper bridge arm and a lower bridge arm), three filter capacitors and three filter inductors; wherein, the positive electrode of the power supply is connected to one end of the contactor S1, the other end of the contactor S1 is connected in series with one end of the contactor S2, and the contactor S2 is also connected in parallel with a resistor; the capacitor C1 and the capacitor C2 are connected in series, the positive electrode of the capacitor C1 is connected to the other end of the contactor S2, and the negative electrode of the capacitor C1 is connected to the positive electrode of the capacitor C2 The negative terminal of capacitor C2 is connected to the negative terminal of the power supply; 6 IGBTs are connected in parallel, the positive terminal of each IGBT is connected to the positive terminal of capacitor C1, and the negative terminal is connected to the negative terminal of capacitor C2, wherein T1 and T2 are a group, and the output terminals of T1 and T2 are connected together; T3 and T4 are a group, and the output terminals of T3 and T4 are connected together; T5 and T6 are a group, and the output terminals of T5 and T6 are connected together; the output terminals of each group are respectively connected in series with filter inductors L1, L2, and L3; the filter capacitors are respectively connected in parallel after the filter inductors.

[0078] The two contactors are connected in series, and the S2 contactor is also connected in parallel with a resistor as a pre-charging resistor; the capacitor is connected in parallel after the contactor as a supporting capacitor, followed by 6 parallel IGBTs, of which T1 and T2 are a group, T3 and T4 are a group, and T5 and T6 are a group; each group receives the same PWM signal, and each group is followed by a series filter inductor and a parallel filter capacitor as a filter. The IGBTs are grouped in pairs to increase the overcurrent capacity of each phase, expand the heat dissipation area of ​​the IGBT, and enhance reliability and safety.

[0079] The functional block diagram of the control unit is as follows: Figure 4 As shown; MCU monitors the status of the main and standby fans in the mine, and communication uses RS-485 communication; the system has error diagnosis and protection in both software and hardware; the ADC signal comes from the information acquisition module; the PWM drive control signal is sent by the MCU and converted into a PWM signal for driving the IGBT through the optocoupler isolation module.

[0080] The charging unit is composed of a 1140V / 380V step-down transformer and a DC charger. The input end of the DC charger is connected to the tap of the low-voltage side of the step-down transformer, and the output end is connected to the battery part. When the regular and standby ventilators in the coal mine are working normally, the charging unit charges the battery part, and the function is realized to achieve "self-charging after power feeding and stopping when full". It is strictly forbidden to float charge or overcharge the battery pack for a long time to ensure that the battery pack is always in good condition for standby.

[0081] The battery part is specifically a 320V lead-acid battery composed of 160 lead-acid batteries connected in series that meet the coal mine safety regulations; the battery management unit adopts an ordinary coulomb meter battery management system.

[0082] The information acquisition unit is specifically a collection of sensors such as voltage, current, temperature, wind speed, etc., and the information acquisition unit transmits the signals to the control unit after collating them;

[0083] The control unit is specifically an MCU, which adopts STM32F407ZET6. It is connected with other well-known devices through the MCU to respectively form a communication circuit, a control signal output circuit, an ADC signal acquisition circuit, a PWM drive control signal circuit, an error diagnosis and protection circuit, etc.; the communication circuit is an RS-485 communication circuit, which is respectively connected to the battery part, the display unit, and the key unit; the control signal output circuit is connected to the charging unit and the battery part; the ADC signal acquisition circuit is connected to the information acquisition unit, and the PWM drive control signal circuit is connected to the inverter unit; the error diagnosis and protection circuit is connected to the inverter unit.

[0084] The display unit is specifically an industrial-grade programmable color screen;

[0085] The key unit is specifically a 16-way input and output motherboard;

[0086] The local ventilator is specifically a corresponding fan in an underground coal mine, which is distributed in the underground excavation working face of the coal mine.

[0087] The software and protocols involved in the present invention are all known technologies.

[0088] The present invention provides an emergency energy storage power supply system for local ventilators in coal mines. The system can solve the problem of gas accumulation after power outages and ventilation in coal mines, and maintain ventilation at the working face. The system is installed at the underground excavation working face of a coal mine as a backup plan for underground power grid or fan failure; the system self-start time can be set according to the actual situation based on the power grid and the status of the standby fan.

[0089] A step-up transformer unit is added to the topological structure of the present invention; the transformer ratio is 220V / 660V or 380V / 1140V; the low voltage side is star-connected, and the high voltage side is a selectable mode: when the output is selected to be 660V, the high voltage side is star-connected; when the high voltage side is selected to be 1140V, the high voltage side is delta-connected. Adding a step-up transformer can reduce the DC bus voltage, thereby reducing the volume of the battery, increasing the flexibility of the system, and reducing the cost of system production.

[0090] When the two power supply systems or the regular and standby ventilation fans fail in the mine, the present invention starts the device and puts it into operation as an emergency device. When the inverter unit is working, the inverter unit adopts an improved five-stage vector control algorithm to provide a control process algorithm for the inverter unit to drive the local ventilation fan of the coal mine. The algorithm adopts five-stage vector control, and the carrier frequency is 5KHz, which reduces the heat generated by the IGBT when the system is working; the improved V / F soft start algorithm is adopted in the motor starting mode, first the voltage frequency is fixed to 10Hz, and the output voltage amplitude gradually increases; when the voltage effective value increases to 132V, the voltage and frequency increase to 660V and 50Hz at a certain voltage-frequency ratio.

[0091] The control algorithm has been improved to suit transformer control.

[0092] The control method adopts five-stage vector control. The specific steps are:

[0093] The three-phase electricity whose magnitude changes sinusoidally with time and whose time phase differs by 120° is synthesized into a spatial voltage vector U ref The first step of space vector modulation is to determine the α , U β The sector where the spatial voltage vector is located is determined by the derivation. The voltage vector U ref The sector is completely controlled by U β , The three formulas determine:

[0094]

[0095] Among them, U α , U β are the coordinate axes in the stationary coordinate system after CLARK transformation, and U1, U2, and U3 respectively determine the voltage vector U ref The judgment value of the sector.

[0096] Now define U1>0, A=1, otherwise A=0; U2>0, B=1, otherwise B=0; U3>0, C=1, otherwise C=0; the formula for judging the sector is:

[0097] N=4*C+2*B+A (2)

[0098] Where N is U ref The sector number; According to formula (2), the voltage vector U ref After the sector is determined, the action time of the basic space vector of each sector can be calculated through Table 1. Table 1 is as follows.

[0099] Table 1 Action time of basic space vectors in each sector

[0100]

[0101]

[0102] Among them, T S is the time for one cycle of vector action, T1, T2, T3, T4, T5, T6 are the time for each vector action in each sector, U dc is the DC bus voltage, T x is the first vector action time in each sector, T y is the vector action time that occurs later in each sector;

[0103] According to formula (3), the PWM duty cycle corresponding to each period of time is calculated:

[0104]

[0105] Among them, NTPWM is the automatic reload value generated by the MCU for the PWM interrupt; T Nx The PWM duty cycle converted from the first vector action time in each sector; T Ny The PWM duty cycle converted from the vector action time in each sector.

[0106] Then, the PWM duty cycle of each phase IGBT of the inverter unit is calculated according to formula (4).

[0107]

[0108] Among them, N taon N is the duty cycle of the A-phase IGBT receiving PWM; tbon N is the duty cycle of the B-phase IGBT receiving PWM; tcon The duty cycle of the C-phase IGBT receiving PWM.

[0109] The MCU calculates the on-time of each phase switch, determines the duty cycle of the MCU output PWM, and transmits the calculated six-way PWM to the 12 IGBT modules of the inverter module (the two upper bridge arms of each phase receive the same PWM, and the lower bridge arms receive the same PWM) to enable the inverter module to invert and output three-phase AC power. When the two power supply systems underground or the regular and standby ventilation fans fail, the equipment is started and put into operation as an emergency equipment to drive the local ventilation fan of the coal mine to work.

[0110] In order to fit the transformer control method, the traditional V / F start is improved. The traditional V / F control is that the voltage and frequency increase in a certain proportion. Because when the input voltage frequency of the transformer is 0, the transformer is short-circuited, the traditional V / F is now improved. Starting with a fixed frequency (taking 10Hz as an example), the voltage gradually increases to a certain voltage amplitude, and then the voltage amplitude frequency increases to the required voltage at a certain ratio. For example, the required voltage is 50Hz and the amplitude is 660V. The relationship between voltage and frequency is as follows Figure 5 shown.

[0111] The above algorithm is written as a program and burned into the MCU. When the main and standby fans underground are powered off or fail, the emergency energy storage power supply system of the local ventilation fan in the coal mine is started in time. The above algorithm is used to start the local ventilation fan in the coal mine in time to ventilate the coal mine working face.

[0112] The system workflow is as follows Figure 6 As shown. ( Figure 6 The solid line in the middle is the direction of the workflow, and the dotted line is the direction of the electrical signal)

[0113] The workflow is as follows:

[0114] Step 1: Check if there is a fault:

[0115] The voltage sensor and current sensor in the information collection unit collect the status of the main and standby power supply in the coal mine in real time, and transmit the information to the control unit (MCU), which determines whether there is a fault; the MCU determines whether the voltage sensor has an AC voltage greater than 600V. If it does, the main and standby power supply is not faulty, otherwise the main and standby power supply is faulty;

[0116] When the main and standby power supplies in the coal mine are fault-free, the transformer high-voltage side tap contactors in the transformer unit, B1, B2, B3 are closed, and A1, A2, A3 are disconnected; at this time, the transformer high-voltage side is connected in a triangle, used as a step-down transformer, to power the DC charger, and the charger charges the battery; the battery is always in a floating charge state, and when the battery power is within a certain range, the MCU controls the contactor to stop charging;

[0117] When the main and standby power supplies in the coal mine fail, run step 2;

[0118] Step 2: The control unit (MCU) controls the transformer high-voltage side tap contactors A1, A2, A3 in the transformer unit to close, and B1, B2, B3 to disconnect. At this time, the transformer high-voltage side is star-connected, and the output voltage of the inverter module is inverted; the MCU controls the contactors S1 and S2 of the inverter unit to close, and pre-charge the capacitors C1 and C2 for energy buffering;

[0119] Step 3:

[0120] Step 3.1: After the contactor of the inverter unit is closed, the control unit (MCU) synthesizes the three-phase electricity with a time phase difference of 120° into a space voltage vector U ref MCU calculates formula (1) and formula (2) to determine the space voltage vector U ref Sector in which you are located;

[0121]

[0122] Among them, U α , U β are the coordinate axes in the stationary coordinate system after CLARK transformation, and U1, U2, and U3 respectively determine the voltage vector U ref The judgment value of the sector;

[0123] Define U1>0, A=1, otherwise A=0; U2>0, B=1, otherwise B=0; U3>0, C=1, otherwise C=0; the formula for judging the sector is:

[0124] N=4*C+2*B+A (2)

[0125] Step 3.2: MCU calculates the action time of the basic space vector of each sector according to the relationship between the action time of the basic space vector of each sector:

[0126]

[0127]

[0128] Among them, T S is the time for one cycle of vector action, T1, T2, T3, T4, T5, T6 are the time for each vector action in each sector, U dc is the DC bus voltage, T x is the first vector action time in each sector, T y is the vector action time that occurs later in each sector;

[0129] According to formula (3), the PWM duty cycle corresponding to each period of time is calculated:

[0130]

[0131] Among them, NTPWM is the automatic reload value generated by the MCU for the PWM interrupt; T Nx The PWM duty cycle converted from the first vector action time in each sector; T Ny The PWM duty cycle converted from the vector action time in each sector.

[0132] Then, the PWM duty cycle of each phase IGBT of the inverter unit is calculated according to formula (4).

[0133]

[0134] Among them, N taon N is the duty cycle of the A-phase IGBT receiving PWM; tbon N is the duty cycle of the B-phase IGBT receiving PWM; tcon The duty cycle of the C-phase IGBT receiving PWM.

[0135] The action time of each sector space vector is converted into the duty cycle of PWM, that is, the improved V / F five-stage vector control algorithm is adopted to generate 6-channel PWM;

[0136] Step 3.3: Transmit 6 PWMs to 12 IGBTs. The two upper bridge arms of each phase receive the same PWM, and the lower bridge arms receive the same PWM. The inverter module inverts the DC power output by the battery into three-phase AC power with a certain voltage amplitude and transmits it to the transformer.

[0137] The inductance and capacitance of the inverter module and the inductance of the transformer form an LCL filter, which filters the voltage output by the IGBT to generate alternating current with a phase difference of 120° on the three phases to drive the local ventilator to work.

[0138] The voltage and current sensors collect the voltage and current information of the local fan in a closed loop, and adjust the speed of the local fan in real time, saving battery power while ensuring the ventilation volume.

[0139] Embodiment 1,

[0140] The following are the functional test results of this system, in which the battery part, status display unit, step-up transformer unit, and inverter unit are the main functional tests of the device;

[0141] Table 2 Basic functional test

[0142]

[0143] The present invention utilizes a transformer to boost voltage, utilizes the inductance of the transformer to perform filtering, and indirectly controls the motor by controlling the transformer, thereby time-division multiplexing the transformer. Although the transformer is a well-known device, the structural circuit of the transformer, the time-division multiplexing circuit, and the indirect control of the motor by the transformer have made changes to the structure of the traditional inverter.

[0144] Battery section The battery management module displays the battery status and sends information to the control unit.

[0145] The status display unit displays information such as output voltage, output current, fan speed, system temperature, main and standby fan status, etc. Display is complete.

[0146] The system's loaded output line voltage is 697.65V, 697.45V, 697.68V, the frequency is 50.26Hz, the three-phase voltage phase difference is 120°, there is basically no harmonics, the output voltage distortion rate is 0.77%, the waveform is consistent with the sine wave, there is no jitter, the effect is as shown in the figure Figure 6 , 7 , Figure 8 As shown, it meets the requirements.

[0147] According to the test results, all system functions have been realized.

[0148] Matters not covered by the present invention are known technologies.

Claims

1. An emergency energy storage power supply system for a local ventilation fan in a coal mine, characterized in that the system comprises a battery part, an inverter unit, a transformer unit, an information collection unit, a charging unit, a control unit, a display unit, a button unit and a local ventilation fan; The connection relationship is as follows: the control unit is connected to the battery part, the display unit, the key unit, the information collection unit, the charging unit, and the inverter unit respectively; the battery part, the inverter unit, the transformer unit, and the local ventilator are connected in sequence; the information collection unit is also connected to the battery part, the inverter unit, the transformer unit, and the local ventilator respectively; the battery part is connected to the charging unit; In the transformer unit, the transformer ratio is 220V / 660V or 380V / 1140V; its composition is that U1, V1, W1 are the taps on the low-voltage side of the transformer, which are star-connected; U2, V2, W2 are the taps on the high-voltage side of the transformer, when the contactors A1, A2, A3 are closed, the high-voltage side is star-connected, and when the contactors B1, B2, B3 are closed, the high-voltage side is delta-connected; The inverter unit includes two contactors S1 and S2, two capacitors C1 and C2, six IGBT modules, three filter capacitors and three filter inductors; wherein, The positive electrode of the power supply is connected to one end of the contactor S1, the other end of the contactor S1 is connected in series to one end of the contactor S2, and the contactor S2 is also connected in parallel with a resistor; the capacitor C1 and the capacitor C2 are connected in series, the positive electrode of the capacitor C1 is connected to the other end of the contactor S2, the negative electrode of the capacitor C1 is connected to the positive electrode of the capacitor C2, and the negative terminal of the capacitor C2 is connected to the negative electrode of the power supply; the 6 IGBTs are connected in parallel, the positive electrode of each IGBT is connected to the positive electrode of the capacitor C1, and the negative electrode is connected to the negative electrode of the capacitor C2, wherein T1 and T2 form a group, and the output ends of T1 and T2 are connected together; T3 and T4 form a group, and the output ends of T3 and T4 are connected together; T5 and T6 form a group, and the output ends of T5 and T6 are connected together; the output ends of each group are respectively connected in series with the filter inductors L1, L2, and L3; the filter capacitors are respectively connected in parallel after the filter inductors.

2. The coal mine local ventilation fan emergency energy storage power supply system as claimed in claim 1, characterized in that the charging unit is composed of a 1140V / 380V step-down transformer and a DC charger, the DC charger input end is connected to the step-down transformer low-voltage side tap, and the output end is connected to the battery part; The battery part is specifically a 320V lead-acid battery composed of 160 lead-acid batteries connected in series that meet the coal mine safety regulations.

3. The coal mine local ventilation fan emergency energy storage power supply system as described in claim 1 is characterized in that the display unit is a TFT color screen, and the key unit is a 485 bus 16-way input and output motherboard; both use RS-485 communication.

4. The method for operating the emergency energy storage power supply system for a local ventilation fan in a coal mine according to claim 1, characterized in that it comprises the following steps: Step 1: Check if there is a fault: The voltage sensor and current sensor in the information collection unit collect the status of the main and standby power supply in the coal mine in real time, and transmit the information to the control unit MCU, which determines whether there is a fault; the MCU determines whether the voltage sensor has an AC voltage greater than 600V. If it exists, the main and standby power supply is not faulty, otherwise the main and standby power supply is faulty; When the main and standby power supplies in the coal mine are fault-free, the transformer high-voltage side tap contactors in the transformer unit, B1, B2, B3 are closed, and A1, A2, A3 are disconnected; at this time, the transformer high-voltage side is connected in a triangle, used as a step-down transformer, to power the DC charger, and the charger charges the battery; the battery is always in a floating charge state, and when the battery power is within a certain range, the MCU controls the contactor to stop charging; When the main and standby power supplies in the coal mine fail, run step 2; Step 2: The control unit MCU controls the transformer high-voltage side tap contactors A1, A2, A3 in the transformer unit to close, and B1, B2, B3 to disconnect. At this time, the transformer high-voltage side is star-connected to invert the output voltage of the inverter module; the MCU controls the contactors S1 and S2 of the inverter unit to close, and pre-charge the capacitors C1 and C2 for energy buffering; Step 3: Step 3.1: After the contactor of the inverter unit is closed, the control unit MCU synthesizes the three-phase electricity with a time phase difference of 120° into a space voltage vector U ref MCU calculates formula (1) and formula (2) to determine the space voltage vector U ref Sector in which you are located; in, U α , U β are the coordinate axes in the stationary coordinate system after CLARK transformation, and U1, U2, and U3 respectively determine the voltage vector U ref The judgment value of the sector; Define U1>0, A=1, otherwise A=0; U2>0, B=1, otherwise B=0; U3>0, C=1, otherwise C=0; the formula for judging the sector is: N=4*C+2*B+A (2) Step 3.2: MCU calculates the action time of the basic space vector of each sector according to the relationship between the action time of the basic space vector of each sector: Among them, T S is the time for one cycle of vector action, T1, T2, T3, T4, T5, T6 are the time for each vector action in each sector, U dc is the DC bus voltage, T x is the first vector action time in each sector, T y is the vector action time that occurs later in each sector; According to formula (3), the PWM duty cycle corresponding to each period of time is calculated: Among them, NTPWM is the automatic reload value generated by the MCU for the PWM interrupt; T Nx The PWM duty cycle converted from the first vector action time in each sector; T Ny The PWM duty cycle converted from the vector action time in each sector; Then, the PWM duty cycle of each phase IGBT of the inverter unit is calculated according to formula (4); Among them, N taon N is the duty cycle of the A-phase IGBT receiving PWM; tbon N is the duty cycle of the B-phase IGBT receiving PWM; tcon The duty cycle of the C-phase IGBT receiving PWM; The action time of each sector space vector is converted into the duty cycle of PWM, that is, the improved V / F five-stage vector control algorithm is adopted to generate 6-channel PWM; Step 3.3: Transmit 6 PWMs to 12 IGBTs. The two upper bridge arms of each phase receive the same PWM, and the lower bridge arm receives the same PWM. The inverter module inverts the DC power output by the battery into three-phase AC power with a certain voltage amplitude and transmits it to the transformer. The inductance and capacitance of the inverter module and the inductance of the transformer form an LCL filter, which filters the voltage output by the IGBT to generate alternating current with a phase difference of 120° on the three phases to drive the local ventilator to work.

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